Apparatus for use at low temperatures



May 26, 1936. A.-B'. |NZE| APPARATUS FOR USE AT Low TEMPERATURES vFiled uarch 11, 19:53 I

M f 70, ///,l i 7 Ox/ ZZ 4 /W 7% /fw/ m ,H/ ,Z0 .//fU M b /2 /////J/ 9/ ,wl f 5,0 Wl f5 ///////0 00 //,MN /////0 Z 4%/ Patented May 26, 1936 UNITED STATES PATENT oFFicE APPARATUS Foa USE A'r `Low TEMrmTvnEs Augustus Braun Kinzel, Flushing, N. Y., assiznor, by mesne assignments, to Union Carbide and garllzon Corporation, a corporation of New Application Maren 11, 193s, serial No. senses 4 clams, .(ci. zzo-9) brittled at the low temperatures encountered.

'Ihe invention has for its objectl generally the provision Vof improved apparatus of the character indicated which is strong and durable both at atmospheric temperatures and at the temperatures of the liquefied gas being handled, for example at the temperature of liquid air or oxygen.

It is also an object to provide improved apparatus such as containers for handling liquefied gases fabricated of an alloy that is characterized by -the possession of mechanical strength and ductility and relatively high Izod values when subjected to impact at very low temperatures.

Still another object is to provide improved compositions for alloys for use in apparatus of the character indicated lwhich do not have notch-brittleness at very low temperatures, for example at *150 C. or 123 Kelvin (hereinafter denoted degrees K.), and which are free from internal stresses at such low temperatures.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the fea.- tures of construction, combination of elements, and arrangement of parts, which will be exempliied in the construction hereinafter set forth and the 'scope of the application of which will be indicated in the claims.

For a full understanding of the nature and bjects of the invention, reference should be had to the following detailed description taken vin connection with'the accompanying drawing, in which:

'Ihe gure depicts exemplary apparatus in vertical cross-section, particularly a container for liquid oxygen, made in accordance with the invention.

It is generally impracticable to connne large quantities of liqueiled gases of the character indicated in completely closed vessels, though it is possible to corinne them within pressure vessels or containers provided with relief valves or other means for preventing the building up of excessive pressures. When this is done, gas pressures of the order of 100 pounds per square inch and above may be safely attained within the apparatus. Considerable difficulty, however, is involved in finding a material suitable for use in the construction of such apparatus.

Heretofore, two materials have generally been employed, such as steel and copper. The disadvantage in the use of steel is that-it becomes exceedingly brittle at temperatures below about 223 K. (or .-50 C.). 1f there are any lockedup stresses in the articles, due to the conditions of fabrication, the additional stresses set up during the chilling of the article to the temperature of liquid oxygen may be sufcient to cause the :failurev of the embrittled steel. For this reason, very careful annealing has been practiced in making such apparatus. Even if such annealing is employed and all lockeduup stresses .are removed, however, the extreme brittleness of the steel renders it highly sensitive to yshock. and vibration at these low temperatures. For this reason, the steel article must be specially supported to e the danger of shock vibration.

Copper has the advantage of remaining ductilel at the temperatures encountered in dealing with liqueed gases of the character indicated. Copper, however, has serious disadvantages, in that, if free from-strains, it has practically no plasticfree elasticity and does not completely return to shape after the removal of an imposed stress.

It gradually stretches with a corresponding reduction in cross-section. Thus, if a vessel of copper or other article of such composition becomes deformed, a failure may occur when it is again put under pressures which it could safely have withstood when new. To avoid this sort of failure, it has been proposed to measure the article under stress, but this is not always practical, and

in any event a deformed vessel is no longer suitable for its original purpose.

In the practice of the present invention, preferably those parts of the apparatus which are subject both to stress and a very low temperature are made of a' metal alloy having substantial freedom from internal stress at such temperature. Referring to the drawing, I0 denotes a 'thick-walled outer vessel of containing appara- 45 tus for liquefied gases, which may be made of welded metal sections, and has a spaced inner lining or basket il which holds a body l2 of the liqueed gas, for example, liquid oxygen. The vessel is provided with suitable uid manipulating connections, for example, a gas-phase withdrawal connection i3 and a liquid-phase withdrawal connection I4, together with a filling connection, as shown at I5.

The vessel IG is preferably enveloped with heat 4at the other to a ring I9 that embraces the vessel. In the apparatus illustrated, the vessel l0, and such other parts as may be desired are fabricated of a metal alloy having substantialfreedom from internal stress at the temperature of -liquid oxygen.

A metal alloy, which has the desired freedom from internal stresses and is suitable for making such vessel and other desired parts, may be prepared in a variety of ways, for example, by dispersing a small amount of a component in a main metallic mass possessing the desired ductility, the dispersion being such as to interfere with the normal slip of the planes of the main metallic lattice when subject to stress. This effects strengthening of the lattice. When the precipitated particles are suillciently fine, local stresses produced by temperature changes from room temperature to a temperature of liquid oxygen are not suiiicent to produce brittleness. If, however, a combination of extremely fine and moderately fine particles is considered, the local stresses are sufficient to affect seriously the low temperature ductlity.

A second way of accomplishing the desired strengthening of non-ferrous materials without necessarily high internal stress, local or otherwise, is to introduce a foreign element into the metallic matrix so that it is in solid solution; that is, it either replaces one of the atoms of the matrix material in the lattice or associates itself by means of electronicvbonds to form a group of one or more metallic atoms which may for-m a secondary lattice, superimposed on the primary lattice. 'Again interference with normal slip is affected and the material is strengthened. In this type, it is most probable that temperature stresses will not be present because of the homogeneous distribution of the two or more types` of atoms involved.

It has generally been found in non-ferrous metallurgical practice that `when a given strengthening mechanism is relied on for more than a relatively small increase, secondary effects take place. 'I'he embrittlement of Duralumin or nickel-suicide-copper, when the precipitation ef.

feet is employed for maximum strength, is. a case in point,'as the ductility is very adversely affected, and it is necessary to limit the strength to an optimum amount to get the desired ductility. Solid solution phenomena are also limited in scope, as frequently if an increase in the amount of foreign atoms is introduced, the tendency to compound formation ,increases with consequent rapid falling off of ductility with increased strength. The oldest recognized method of strengthening metals consists v in forming eutectics by means of a second component.`

Eutectics, in general, will not fill the needs of the alloy in the invention because the heterogeneous nature of a lamellar structure tends to promote' local thermal stresses at low temperatures. However, a comparatively small amount of suitable eutectic may be formed without deleterious eifect if the solid solution matrix is the predominantly continuous phase.

According to the present invention, an alloy is produced in which the strength is higher than that obtainedby any one of the above described ways, particularly with respect to ductility and with respect to elimination of thermal stress when vthe alloy is cooled to liquid oxygen temperature:

the alloy here provided comprising elements so combined that two or lmore of the aforementioned desired eiects are simultaneously obtained.

Themain metallic component of 'the composition used in the present invention thus is a metal which has high ductility throughout substantially the whole range of service temperatures, for example from 100 C. down to and including that of the liquefied low boiling point gases. This is particularly true of the nonferritic empirical group of metals comprising copper, aluminum, and magnesium. Such metallic component is taken in an amount comprising generally more than 90% by weight of the whole metallic composition. Certain alloys of the group are also suitable for the main component or matrix mtal, as are combinations within the above group constituting 90% of the matrix. Zinc brasses or aluminum bronzes, which are chiefly copper, are illustrative. As a speciiic example may be mentioned a. brass which has as its components copper and zinc taken in substantially the ratio of six parts of copper to four parts'of zinc.

As a second component for the metallic composition adapted to form a solid solution with the main metallic component there is employed a metalloid or metallic element, which forms a solid solution with the iirst in the manner of the well known binary systems. A suitable component of this character for the compositions desircd may be chosen from the empirical group consisting of boron, silicon, and beryllium. Sili-V con is preferable because it tends to form compounds with a third metallic component, hereinafter described, when taken in relatively small amounts, forexample 3% of silicon begins to form a eutectic with magnesium, 5% with copper and 1.6% with aluminum. Beryllium forms a solid solution with copper up to 2.8%, but more than vthese amounts'form the eutectic.

A third component may be employed for a composition of metal made according to the present invention, such component being of a character such that it remains in dispersion throughout the metallic mass, either in atomic form or F asv a compound with the 'main combination or one of the secondary combinations and by means of this dispersion effects interference with the slip of the metallic planes in the metallic lattice as previously described. A suitable component for accomplishing this is chosen from the empirical group consisting of manganese, iron, nickel, and

chromium. Manganese is generally preferable because of its action in the metallic bath when preparing the alloy. The manganese is taken in relatively small amounts; for example in amounts approximating not over 4% by weight of the total mass, which isA also true for iron and nickel. Chromium, however, should be vtaken generally in smaller amounts; for example, in amounts in 6 the neighborhood of 2% by weight of the total used with copper. Amounts in excess of the solid amiante solution saturation content-at room` temperature may be used in dispersion strengthening. Likewise, the elements of the second group all form solid solutions with copper Vto more or less limited extent. Moreover, it is possible and may bedesirable to employ Aelements selected from any of these groups to promote strengthening to a limited degree by taking them in suchamounts as to cause the presence. of eutectics,v the relative proportion being substantially small when compared to the amount of base metal matrix used.l Generally, however, this is not desirable., as eutectics are conducive .to the production of thermal stresses at low temperatures.

'Ihe following are examples of compositions made in accordance with the invention:

Example I 1 Per cent Copper I 96 Silicon 3 Manganese 1 Example II Per cent Copper- 58 Zinc 38 Silicon 3 Manganese l Example III l Per cent Magnesium u 98.4 Silicon 1.2 Manganese .4

Example 1V Per cent Copper. 97. I Silicon- .4 Nickel 2.5

Example V Per cent Copper p 98.7 Silicon 3 Chromium 1.04

Example VI Per cent Aluminum 92. 5 Beryllium 1.5 Iron- 3. 0 Manganese-.. 3. 0

Example VII Per cent Copper- 94 Beryllium 6 When tests are made to compare the physical properties of alloys of the above compositions with those of steel, standard specimens are prepared and placed in a testing machine where the ultimate strength is determined vboth at ro'om teme perature and at the temperature to which it will be subjected when in use, for example at K.

'Ihe yield point is similarly ascertained, together which are comparatively set forth in the following table: y

Tests on an alloy of the composition of Example I when subject to Izod impact tests show values at room temperatures of from 58 to, l1,64 foota pounds, while at the low temperature of 90 K. values of from 70 to 78 foot-pounds are obtained. Similar tests with steel of the above composition show Izod values o1' from 35 to 45 foot-pounds at room temperature, while at 90 K. it gave substantially zero values and shattered easily.

Besides high Izod test values, an alloy of the composition of Example I has additionally the desirable properties oi'great ductility and workability, weldability with great strength and toughness of welds, and relatively low heat conductivity ascompared with copper; this latter being in general a property in common with all the alloys proposed in accordance with the invention.

Izod values of the orderl of| 40 foot-pounds are had from standard specimens of an alloy of the composition of Example II at temperatures in the neighborhood of that of liquid air, the ailoys of the other examples giving similar substantialv values at temperatures in the neighborhood of that of liquid air.

From the above, it will be seen that 4the criterion of strength is the usual tensile test and that the criterion for ductility which postulates the absence of internal stresses at low temperature is the Izod value obtained at such temperatures. Hence, it is seen from the above that vthe alloys here proposed for use in apparatus which is subjected to vstress and very low temperatures provide safe apparatus that is substantially free from internal stressesy in the metal composing it when subject to a low temperature such as that of liquid air or oxygen.`

Since certain changes may 'be made in the above construction and diilerent embodiments of the invention could be made without departing from the scope thereof, it is intended that all matter contained ,in the above description or shown in the accompanying, drawing shall be interpreted as illustrative and not in a limiting sense.

Having described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. Apparatus for handling .liquefied gases including a heat insulating envelope and a substantially closed vessel supported within said envelope subjectto a temperature at least as low as 123 Kelvin comprising fabricated metal parts of an alloy consisting of a ductile metallic matrix comprising copper taken in an amount constituting approxirnately.96% of the whole, a second component consisting of silicon taken in an amount constituting approximately 3% of the whole, and a third component consisting oi manganese taken in an amount to constitute the balance; the whole being characterized by the maintenance of mechanical strength, relatively great ductility and relatively high Izod values at a temperature at least as low as 123 Kelvin.

2.A Apparatus for storing and transporting liquid oxygen comprising a heat insulating envelope and a substantially closed liquid containing vessel supported within, said envelope subjected to a temperature in the neighborhood of 90 Kelvin made of sections welded together, said sec` tions and welding material being of an alloy having the following composition; Copper from about 92.5% to about 96.5%, silicon from about 3% to about 6.5% and manganese from about 0.5% to about 1.5%; said alloy being characterized by the properties of sa tensile strength of more than 50,000 pounds per square inch in. .505 inch specimens and an Izod impact value of the order of.60 foot-.pounds per square centimeter when subjected to said temperature.

3. Containing apparatus for storing and transporting liquid'oxygen and the like comprising a heat insulating envelope and a relatively thickwalled vessel ,having an inner lining and an exterior supporting casing, said vessel comprising welded sections of a metallic alloy consisting of brass taken in an amount exceeding 90%, a relatively small amount of manganese, and the balance being silicon, said alloy being characterized by a relatively high tensile strength and an Izod impact value of substantial magnitude when subjected to a temperature in the neighborhood of that of liquid oxygen at normal atmospheric pressure.

4. An implement for use in the handling of a liquefied gas'comprising a containing vessel capable of resisting stress from high pressure and/or from shock at a temperature below 223 Kelvin and made of parts fabricated together, which parts are of an alloy of the three-component variety; the rst component forming a ductile. non-ferrous metallic matrix taken in an amount at least 9.0% by weight of the whole and chosen from the group consisting oi aluminum, aluminum bronze, magnesium, copper, and brass; the second component being a strengthening agent dispersed in the rst andchosen from the group` consisting of beryllium, boron, and silicon; the third component being a relatively small amount of an element imparting slip interference and. chosen from the group consisting -of chromium, nickel, iron, and manganese; the several components composing said alloy being so combined and compounded as to impart to the alloy when at said low temperature the properties of vrela' tively great mechanical strength', relative absence of internal stress,I and a relatively high Imd value, in comparison with such properties of the alloy when at room temperature. AUGUSTUS BRAUN KINZEL. 

